I'm having massive frustrations with my CMOS battery on my packard bell 486. Wasted a bunch of time yesterday trying to troubleshoot this again.

The person I got the pc from had used pins J28 to attach an external battery pack with 3 AAA batteries, but it wasn't fully working when I got it and I've been failing at every turn to get it to work. Initially, it just seemed like the plug was lose on the pins, and applying some pressure seemed to get it to work. Eventually that stopped working. Then I thought the batteries were loose in the case, so I added some padding to make it tighter and that seemed to work for a bit, but then eventually failed. I changed out the cable with a CDrom audio cable (for snugger fit on the 4 pin), soldered it to the battery packs positive and negative leading to the correct pins on the board, and that seemed to work, then failed later.

Eventually I found that there is another jumper, J24, that needs to be open when using an external battery, I think to prevent the board from sending a current to the battery to recharge? I checked the AAA batteries and the first battery was super dead and two were fully charged, presumably the small current was totally ruining the first battery? Not sure if that's even how it works when using external battery. Removed the jumper, replaced the battery, and everything seemed fine for a long time.

And now, it's failing again. New batteries, tight connection, J24 jumper open, and I get real time clock failure every boot. So exhausted from dealing with this. Sorry for the long story but I'm hoping someone can point me in the right direction of what I should do or check. I'm not very good at diagnosing this stuff. In the meantime I'm just buying a new battery pack and cable and will redo everything from scratch with new materials and see what happens. 🙁